(1) Field of the Invention
The present invention relates generally to underwater acoustic detection devices and specifically to impeller driven electrical generators for self powered devices towed underwater.
(2) Description of the Prior Art
Towed acoustic receptor arrays have found a wide variety of uses throughout both the military and commercial sectors. In military uses, the U.S. Navy has used towed receptor arrays to distance the array from the "noise" of the towing ship. This separation allows the receptor arrays to operate at a higher level of sensitivity leading to earlier detection of hostile targets. In the commercial-sector, many operators have used towed arrays for exploration, notably in the fields of oil and gas exploration and salvage operations. In both these cases, the objective has been to boost the sensitivity of the towed array while distancing it from the towing craft so that the array operation is not affected by the movement of the towing craft. However, the use of the long tow cables has resulted in two major inherent drawbacks. First, the cable itself is subject to electromagnetic interference from a variety of sources, including other devices towed by the same tow cable. Additionally, power is provided for the remote devices from the towing ship. This means that each tow line must contain a copper power feed in addition to the data transmission leads. The drawbacks from this are numerous. The power feed is an additional source of electromagnetic interference for the closely situated data transmission leads. The length of the tow cable is usually of such magnitude that significant amounts of power (up to 50%) are dissipated during transferal of power from the towing ship to the end device. This dissipation requires that larger diameter cables be used to handle higher power levels, which increases the weight of the cable, increase the storage requirements and further complicates the electromagnetic problems already described.
In the prior art, attempts to solve these problems have focused on the data transmission side of the problem. Through the use of fiber optic transmission leads, prior art devices have succeeded in making the transmission media less susceptible to electromagnetic interference, both from the nearby power feed as well as from other, external sources around the tow cable. The use of fiber optic leads has also decreased the amount of copper wiring in the towed cable, thus beneficially decreasing the weight and diameter of the tow cable.
However, the power feed remains a significant problem not yet addressed by the prior art. No prior art devices have eliminated this "weak link" which provides the bulk of the electromagnetic interference and tow cable weight in the prior art.